FIG. 1 depicts a typical sensor apparatus. For example, the resistance value or capacitance value of a sensor device 1 changes depending on a detected physical quantity. A sensor signal-voltage converting circuit 2 converts an output signal which reflects a resistance value or capacitance value of the sensor device 1 to a voltage. An amplifier 3 increases the voltage obtained using the sensor signal-voltage converting circuit 2. The amplifier 3 conventionally has gain adjustment and offset adjustment functions. An output buffer amplifier 8 is supplied with the output voltage of the amplifier 3, and outputs a voltage signal VOUT. With this configuration, the voltage signal VOUT is output in accordance with the physical quantity detected by the sensor device 1.
FIG. 2 depicts the typical output characteristics of the sensor apparatus of FIG. 1. The physical quantity, which may be acceleration, pressure, temperature or the like, input to the sensor device 1 is plotted on the horizontal axis. The output voltage signal VOUT [V] is plotted on the vertical axis. The sensor device 1 is adjusted so that when the input is “0”, i.e. when the physical quantity is at a neutral or reference level, the voltage signal VOUT is a central voltage V0 of the output range. As the input increases or decreases from “0”, the voltage signal VOUT also increases or decreases about the central voltage V0 in the output range of 0 to 5[V].
The typical sensor apparatus depicted in FIG. 1 may require that the output is linear with respect to the input physical quantity. In the typical sensor apparatus depicted in FIG. 1, however, the relationship between the input physical quantity and the output voltage signal VOUT may be non-linear as depicted in FIG, 2 due to the properties of the sensor device 1 itself, scattering of the output, and the like.
In a sensor apparatus for which a linear output like an ideal characteristic may be required, if the voltage output denoted by the voltage signal VOUT strays greatly from the ideal characteristic, the measuring accuracy of the sensor apparatus falls.